A recessive allele in dogs causes white spots.If two solid colored dogs are mated and produce a spotted offspring,what is the percentage chance their next puppy would be solid colored?
A)25%
B)about 90%
C)50%
D)about 66%
E)75%

Question

Quizplus · Accepted Answer

75%Since the spotted phenotype is caused by a recessive allele, both parents must be heterozygous carriers (having one dominant allele for solid color and one recessive allele for spots) to produce a spotted offspring. When two heterozygous carriers are crossed (genotype Rr x Rr), the expected offspring genotype ratio is 1:2:1, which translates to 25% homozygous recessive (rr, spotted), 50% heterozygous (Rr, solid colored), and 25% homozygous dominant (RR, solid colored). Therefore, the chance of producing a solid-colored puppy is 75% (50% heterozygous + 25% homozygous dominant).

A Recessive Allele in Dogs Causes White Spots